Generally speaking, a magnetic recording medium such as a magnetic tape is prepared by coating a magnetic coating liquid containing a magnetic powder, a binder resin, and the like on a support and then drying.
In such a magnetic recording medium, particularly in video tape, carbon black is used with the magnetic powder in order to satisfy simultaneously some of requirements such as conductivity, coefficient of friction, surface characteristic (i.e., electromagnetic conversion property), wear resistance, etc. As techniques of this kind, there are conventionally known those disclosed in Japanese Patent Publication Open to Public Inspection (hereinafter referred to as O.P.I.) Nos. 5426/1984, 16141/1984, 218039/1983 and 211321/1983, Japanese Patent Examined Publication Nos. 20203/1978, 9041/1979 and 4968/1982.
Also, O.P.I. No. 144727/1986 discloses a magnetic recording medium having a magnetic layer containing a ferromagnetic alloy powder, wherein the magnetic layer also contains a fatty acid having a melting point of less than 50.degree. C., a fatty acid and a fatty acid ester having a melting point of not less than 50.degree. C., and a carbon black having an average particle size of from 60 to 120 nm and a DBP oil absorption of not more than 100 ml/100 g.
In a conventional magnetic recording medium, however, the ferromagnetic alloy powder used in combination with the carbon black had been limited with respect to its surface area but not restricted with respect to its composition. However, in recent years, uses of video tape have been diversified as portable-type video recorder-player units come into common use, so that the video tape is being used under a wide variety of conditions. Accordingly, the video tape is required to be highly corrosion-resistant. Among the ferromagnetic alloys whose corrosion resistance would be expected to fall into the desired range, iron-aluminum-type ferromagnetic alloys suitable corrosion resistance. Moreover, iron-aluminum ferromagnetic alloys, unlike ferromagnetic alloys in general, have good dispersability.
In conventional magnetic recording mediums, the addition of an iron oxide-type magnetic powder and carbon black to a magnetic layer is known, but the optimum conditions for the use in the magnetic layer of the ferromagnetic alloy metal powder in combination with carbon black has been an object of research and development.